316 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1919. 
dependent upon the agriculture of people who live thousands of miles 
away, on other sides of the globe. Facilities of communication make 
the agricultural problem universal, though production still is limited 
by the same factors as in primitive times. Forests and soils continue 
to be depleted. Production is not maintained indefinitely on the 
same lands, but new regions are opened and exploited. Our agri- 
culture must, still be described as predatory and temporary, rather 
than as constructive and permanent. Unnecessary transportation 
wastes labor and other productive resources in civilized countries no 
less than among the primitive people who find themselves compelled 
to move to, new lands when old locations become denuded and grass- 
grown. 
The removal of population from a denuded district might be 
gradual, or there might be a general withdrawal to a new settlement 
in the midst of fertile lands and with an abundance of fuel close at 
hand. Thus it is not difficult to understand that a center of popula- 
tion in one period might a little later be completely abandoned and 
allowed to grow up again to forests. The Indians of Central 
America are extremely conservative, stationary people, who would 
resist any change as long as possible, but once such a movement had 
definitely begun the tendency would be for the whole population to 
go, so as to maintain a strong community. From this point of view 
the traditions of prehistoric migrations and colonization of new dis- 
tricts do not seem strange or unreasonable. 
Tn recent centuries, during the period of exploitation by Europeans, 
the normal relations between the native system of agriculture and its 
environment have been altered in many ways. Populations have 
often been restricted, reduced, or compelled to move by wars, political 
disturbances, or economic changes, and the agricultural systems of 
many districts have been altered profoundly by the introduction of 
beasts of burden and grazing animals. Grass lands that were useless 
before became available as pastures. (See pl. 18, fig. 1.) In some 
districts grazing may reduce fires and thus assist reforestation, but in 
the tablelands of Guatemala the danger of erosion seems to have been 
increased by close grazing. (See pl. 12.) 
PRECAUTIONS AGAINST THE SPREAD OF FIRES, 
Primitive peoples would hardly be aware of the limitations of the 
milpa system or make conscious efforts to maintain a balance with 
the natural conditions to insure a food supply for future generations. 
Within its own sphere of influence each family chooses annually the 
most promising place for its cornfield, with little or no regard to the 
outlook for subsequent years. To foresee the ultimate effects of this 
policy from the standpoint of the community and enforce measures 
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